Flat panel display has been widely used in applications for displays with a higher resolution, a wider color gamut and more response speed. As humans desire that the most natural, most realistic, and a stereo images may be shown ultimately, so the stereo/three-dimensional (3D) image display technology has been considerable emphasis.
The original idea of the three-dimensional stereoscopic display technology is that the left and right eyes are accepted different images, respectively. Generally speaking, relative position of objects in space is determined correctly by the combination of a number of depth cues. The depth cues include binocular parallax, adaptation of the human eye, motion parallax, perspective, the size relationship between observing objects, material of objects. That is, the stereoscopic display must have at least two characteristics of the binocular disparity and motion parallax, wherein the depth of information is more accurately determined by the binocular disparity. Due to a displacement (interval about 65 mm) between two eyes in the horizontal direction, binocular disparity is created such that images seen by two eyes have a slightly different, and therefore, contents of the received image are also slightly different. The motion parallax indicates as the viewer's eye position moves, because viewing angle changed, the contents of the eye received are also different. Therefore, to receive three-dimensional image, individual images received by the left eye and right eye, respectively must be allowed only slight differences, and then fused into the brain to create the three-dimensional images with depth information. Currently, reconstruction for the 3D display stereo images are mostly designed based-on binocular disparity, wherein the images with different viewing angles are projected onto the left and right eye by using a special optical design, and then through the brain integrating the two images, which can be reconstructed the stereo images.
In the early, three-dimensional image display is mostly wearing glasses type stereoscopic display. Shutter glasses 3D display rate is playing images of the left and right eye viewing angles by refresh frequency 120 Hz or more. When the display is showing the left eye's frame, the left eye shutter glass will be open, and the right eye is covered. When the display is showing the right eye's frame, the right eye shutter glass will be open, and the left eye is covered. With fast switching the left and right eye information, the left eye and the right eye can see the correct frame (picture), respectively. After a persistence of vision with the visual integration by the brain, it can be showing the stereo depth image.
However, the above-mentioned wearing glasses type stereoscopic display needs to wear the special equipment which will often impede the nature vision of human. Therefore, in recent years, a naked-eye stereoscopic image display is gradually developed. The naked-eye 3D display can be implemented by two types of the time multiplexing and spatial multiplexing. Time multiplexing is utilized by a directional backlight and a fast response panel, quickly displaying the left and right eye images such that the viewer's left and right eye can see left and right eye images, respectively. Spatial multiplexing is to show the left and right eye images simultaneously, at the expense of the frame resolution, which is implemented by the Parallax barrier and the Lenticular lenses. The parallax barrier is utilizing a grating to control the forward direction of light, while the Lenticular lens is using a different refractive index to control the direction of light.
Moreover, cylindrical lens is composed of many thin straight strip convex lens arranged in a row along one axis direction, which generates different views of the left and right eyes by an light refraction, and which is utilizing light refraction to achieve the purpose of splitting, less loss of light and better brightness. However, as the production error, surface irregularity of cylindrical lens or other factors, there will generate stray light, which leads to some vague three-dimensional images, and thus affecting the overall 3D image display. Besides, the parallax barrier is used to restrict the light emitting out of certain angle by using the whole barriers, and only view images in specified angle send to the right and left eyes, respectively, to produce three-dimensional images.
Moreover, a conventional three-dimensional display device can only show three-dimensional images, but without switching between the plane (two dimensional) images and the stereo (three dimensional) images. Therefore, a stereo images display device has been developed for switching to display three-dimensional images and the plane images. Currently, a general localization 2D/3D switching technology is mainly using Parallax barrier and the Lenticular lenses. Parallax barrier and the Lenticular lenses can be placed in the front of the display panel or placed between the display panel and the backlight module. For example, a switchable 2D/3D parallax barrier display comprises a parallax barrier 102, a display panel 101 and a backlight module 100, shown in FIG. 1a and FIG. 1b. The parallax barrier 102 is disposed in the front of the display panel 101. When the image contents display as 3D images in some regions, it produces the parallax grating effect on the corresponding region 102a, namely, the 3D display mode, shown in FIG. 1a. When the image contents display as 2D images, the parallax grating effect disappears on the corresponding location (region) 102b, shown in FIG. 1b. The left eye and the right eye are seen the same pixel, as the same normal 2D display. Another mode is 2D/3D switchable display Lenticular lens, which has similar functions with the 2D/3D switchable Parallax barrier display. In such case, in the 2D/3D switchable display Lenticular lens, the Lenticular lenses 103 replaces the Parallax barrier 102, shown in FIG. 2a and FIG. 2b. The Lenticular lenses 103 is disposed in the front of the display panel 101. When the image contents display as 3D images in some regions, it produces the Lenticular lens effect on the corresponding region 103a, namely, the 3D display mode, shown in FIG. 2a. When the image contents display as 2D images, the Lenticular lens effect disappears on the corresponding location (region) 103b, shown in FIG. 2b. The left eye and the right eye are seen the same pixel, as the same normal 2D display.
In the 2D/3D switchable Parallax barrier display, as the liquid crystal has the intrinsic ability to make light penetrating or not, it is one of the easiest way to achieve the regional Parallax barrier by using the LCD panel. For example, in a 2D/3D switchable Parallax barrier display, two LCD panels are disposed in the front of the backlight module, which the first LCD panel is as the parallax grating. When the display panel is to display 3D contents, black and white stripes are displayed on the corresponding areas of the front LCD panel. When the display panel displays 2D contents, white frames, complete penetration of light, are displayed on the corresponding areas of the front LCD panel. Therefore, the displaying contents of the front LCD panel can be controlled to achieve the switching function of 2D/3D regionalization.
In the 2D/3D switchable Lenticular lens display, it includes regionalization 2D/3D switching Lenticular lens, which includes two types switching LCD panel, active switching Lenticular lens LCD panel and passive switching Lenticular lens LCD panel. For example, the active switching Lenticular lens display technology is well developed by Philips Corporation. Liquid crystal is poured into the internal of a columnar lens (eg, concave lens) 114, and enclosed by the upper and lower glass substrates 115 and 112, and a polarization film 111 is configured under the lower glass substrate 112 and display pixels 110 are disposed under polarization film 111. As the liquid crystal is a birefringent material (refractive index N and n), which can by applied a voltage (V) to change its refractive index. The appropriate refractive index of the liquid crystal material may be chosen to match with a refractive index (eg, for n) of the lens 114. When no voltage is applied on the columnar lens 114, the refractive index of the liquid crystal layer is N, different from the refractive index n of the lens, and thereby resulting in a refractive index difference. As the light passes through the active switching columnar lens 114, it will change the propagating direction of light due to the refractive index difference, such creating a 3D mode display, shown in FIG. 3a. When a voltage is applied on the active 2D/3D switching columnar lens 114, alignment of the liquid crystal is changed and the refractive index of the liquid crystal layer 113 is n, the same as the refractive index n of the lens. As the light passes through the display pixels 110, it propagates along the original light incident direction, such creating a 2D mode display, shown in FIG. 3b. Therefore, in such scheme, it is optionally applying the voltage to the columnar lens 114 to generate a 2D/3D switching effect.
In the passive switching Lenticular lens LCD panel scheme, it utilizes a fixed birefringence (refractive index N and n) columnar lens 114 and a switching liquid crystal layer 116 to control the propagating direction of light. This technology is utilized by the switching liquid crystal layer 114 to determine whether the columnar lens 114 works or not, so it belongs to a passive mode of operation. As a voltage does not apply to a switching liquid crystal layer 116, for example TN, assume polarization direction of the incident light passing through the polarization film 111 is changed from zero degree into 90 degree after passing through the witching liquid crystal layer 116. Meanwhile, the refractive index of the liquid crystal layer 113 of the columnar lens 114 is N, different from the refractive index n of the lens, and thereby resulting in an optical path difference. It will change the propagating direction of light to produce a Lenticular lens effect, namely creating a 3D mode display, shown in FIG. 4a. As a voltage is applied to the switching liquid crystal layer 116, alignment of TN liquid crystal is then changed, and polarization direction of the incident light is still zero degree after passing through the switching liquid crystal layer 116. Meanwhile, the refractive index of the liquid crystal layer 113 of the columnar lens 114 is n, the same as the refractive index n of the lens, and without changing the propagating direction of light, namely creating a 2D mode display, shown in FIG. 4b. Therefore, in such scheme, it utilizes a partially controlling the voltage to the witching liquid crystal layer to reach the purpose of a regionalization 2D/3D switching effect.
As above-mentioned, in the conventional 2D/3D switching scheme, Lenticular lens is required to combine at least one liquid crystal layer, and must be applied a voltage to the columnar lens, in order to achieve regional 2D/3D switching effects. Therefore, the manufacturing cost is more expensive, and the scheme is complex and prone to produce bad switching or display. In view of these shortcomings of the traditional scheme, the present invention provides a superior parallax barrier/grating than the prior arts in order to overcome these shortcomings.